The ability of Herpes simplex virus type 1 (HSV1) to cause lesions of the oral cavity is well established. This has made the oral cavity the primary target for investigations concerning the site of latent HSV1 and the level of immune competence of the host. The existing reports on the interaction of herpesvirus and the host response have established that both humoral and cellular immunity participate in control of infection by this virus. However, the state of immunity of patients with herpes has not been examined in vitro, where humoral and cellular responses can be studied in the absence of "host" factors. In such a system the true picture of interaction between HSV1 and immunocompetent cells can be examined. This study will examine immunoresponsiveness of peripheral blood lymphocytes from patients seen in a dental clinic. The role of dental disease in modifying host responses to herpes virus will be investigated by determining the immune reactivity of patients with various forms of oral inflammatory diseases to herpes and other antigens. This will involve testing at two levels: first to determine the nature of the response, i.e. whether humoral and/or cellular; then to determine the effect of the virus on the ability of the patients' lymphoctyes to respond in vitro to a "third party" antigen employing the marbrook culture system. In this manner patients with periodontal or endodontal pathologies 8where there is a heightened local inflammation) will be examined to determine if they respond immunologically, on a systemic level, in a manner similar to normal patients. A third population, immunosuppressed individuals, will be examined also for their responses to HSV1. Since previous reports show differences in the nature of the immune response to HSV1 in experimental animals as compared to humans, the present study will also include a comparison of the responses in the mouse to that seen in man.